The issue with your question, or perhaps your girlfriend's viewpoint, is that it is based off a modern definition of societies that were "progressive." It isn't that simple. They were advanced in their own ways and we cannot use a contemporary meaning of the word.

With regards to Native Americans, many of the native societies were advanced and progressed to lengths in technology and understanding that equaled or surpassed their European counterparts. Check out this thread where it is heavily discussed. The OP in that thread is a mod and historian of this subreddit. He provides sources in his comments and can be asked to provide more if anyone doubts his statements. In that thread, you'll find:

• Many native societies had highly developed agricultural techniques. All tribes did not rely solely on hunting and gathering because they lacked knowledge of farming.

• Many tribes lived in cities that could rival their European counterparts, even surpass them. Nor did they lack the population within these cities.

• Politics and forms of government already existed within these communities.

• Architecture and engineering gave birth to marvels of advancement.

• Pre-Columbian Americans pursued a detailed understanding the world, just as others elsewhere in the world did.

• And these societies certainly did leave the stone age behind. Check here for metallic and lithic technologies.

One thing to understand is this: these Native societies didn't develop certain things other civilizations did because they were "regressive" or "static." It was because their needs were fulfilled by what they had at the time. For example, many tribes did not farm. Many think this is because they lacked an agricultural understanding to sustain themselves that way and chose to hunt and gather because it was easier. However, hunting-and-gathering societies were often vital trading partners with their agricultural neighbors, providing surplus meat, skins, furs, and wild plants for the agricultural products. Though a post-Columbian development, the surge in bison-hunting following the introduction of the horse allowed for the flourishing of many Plains societies, to the point where some like the Cheyenne and Lakota abandoned their former agricultural systems in favor for more economically productive hunting.

In other words, they chose a path that was more beneficial for them at the time. Not because they were progressing at a slower rate than Europeans.